A first order reaction A → B occurs in an isothermal porous catalyst pellet of spherical shape. If the concentration of A at the centre of the pellet is much less than at the external surface, the process is limited by__________________?

Related Mcqs:

1. A spherical porous catalyst particle of radius R is subjected to reactant A which reacts to form B by a zero order surface reaction A → B. Film mass transfer resistance is negligible and pore diffusion of A is rate controlling. The effectiveness factor of the catalyst is reported as 7/8. Which of the following statement is true?

   A. Inner catalyst core of radius R/8 does not participate in reaction
   B. Inner catalyst core of radius R/2 does not participate in reaction
   C. Inner catalyst core of radius 7R/8 does not participate in reaction
   D. Effectiveness factor for a zero order reaction cannot be 7/8 as it must always be 1

2. Second order consecutive irreversible reaction as shown in the bellow figure, were carried out in a constant volume isothermal batch reactor with different initial feed compositions. Reactor temperature was same in all the cases. In experiments where the ratio of concentration of B to that of A in the initial feed was less than 0.5, the concentration of B increased first, reached a maximum and then declined with time. However, for all experiments where this concentration ratio was 0.5 or above, concentration of B decreased monotonically with time right from the beginning. What is the ratio of the two rate constants (k1/k2) ?

   A. 1/4
   B. 1/2
   C. 2
   D. 4

3. Rate constant for a first order reaction does not depend upon reaction time, extent of reaction and the initial concentration of reactants; but it is a function of reaction temperature. In a chemical reaction, the time required to reduce the concentration of reactant from 100 gm moles/litre to 50 gm moles/litre is same as that required to reduce it from 2 gm moles/litre to 1 gm mole/litre in the same volume. Then the order of this reaction is ?

   A. 0
   B. 1
   C. 2
   D. 3

4. Effectiveness factor E. of a catalyst pellet is defined as, E = (actual rate within pore of the catalyst)/(rate if not snowed by pore diffusion), Effectiveness factor for a first order reaction is given by (where, T = Thiele modulus) ___________________?

   A. tan hT/T
   B. tan T/T
   C. tan hT/tan T
   D. None of these

5. For a first order isothermal chemical reaction in a porous catalyst, the effectiveness factor is 0.3. The effectiveness factor will increase if the____________________?

   A. Catalyst size is reduced or the catalyst diffusivity is reduced
   B. Catalyst size is reduced or the catalyst diffusivity is increased
   C. Catalyst size is increased or the catalyst diffusivity is reduced
   D. Catalyst size is increased or the catalyst diffusivity is increased

6. Following isothermal kinetic data are obtained in a basket type of mixed flow reactor for a porous catalyst. Determine the role of pore diffusion and external mass transfer processes ?

   A. Strong pore diffusion control and mass transfer not controlling
   B. Both pore diffusion and mass transfer not controlling
   C. Both pore diffusion and mass transfer controlling
   D. Mass transfer controlling

7. Which of the following factors control the deactivation of a porous catalyst pellet?

   A. Decay reactions
   B. Pore diffusion
   C. Form of surface attack by poison
   D. All A., B. and C.

8. In a chemical reaction, represented by as shown in the bellow figure, it is observed that the (i) Rate of reaction increases by a factor of 4 on doubling the concentration of the reactant. (ii) Rate of reaction increases by a factor of 9 on trebling the concentration of the reactant. Then the rate of the reaction is proportional to(where, CA = concentration of the reactant)_____________________?

   A. CA
   B. CA2
   C. CA3
   D. CA4

9. Overall rate of reaction in a heterogeneous catalytic reaction depends upon the mass and energy transfer from the fluid to solid surface and its rate of reaction is usually ________________ the concentration of catalyst, if it does not entail a chain mechanism?

   A. Proportional to
   B. Independent of
   C. Inversely proportional to
   D. Proportional to the square of

10. In a chemical reaction as shown in the bellow figure, it is observed that the (i) Rate of formation of ‘P’ is doubled on doubling the concentration of ‘X’ (ii) Rate of formation of ‘P’ is quadrupled on doubling the concentration of ‘Y’ (iii) Doubling the concentration of ‘Z’ does not affect the rate of formation of ‘P’ What is the order of the above chemical reaction ?

    A. Zeroth order
    B. First order
    C. Second order
    D. Third order